1. Field of the Invention
This invention relates to an improvement of a dry-type integral multilayer analytical element for analysis of cholesterol contained in an aqueous liquid sample such as blood and other body fluids.
2. Description of Prior Art
Recently, as a dry-type analytical element, integral multilayer analytical elements wherein a water-absorptive reagent layer containing reagents for color-forming reaction and a hydrophilic polymer binder and a porous spreading layer are provided on a light-transmissive support have bean developed. Various samples can be analyzed by using this multilayer analytical element where the reagents are changed, and the multilayer analytical elements for analysis of cholesterol have also been known (Clin. Chem., 28(5), 1159-1162 (1982) and U.S. Pat. No. 4,012,325).
Such a conventional multilayer analytical element for analysis of cholesterol consisted of a light-transmissive support, a gelatin layer and a spreading layer laminated in this order, and necessary reagents such as cholesterol esterase, cholesterol oxidase, peroxidase, a leuco pigment, etc. were added as illustrated in the following (CLIN. CHEM., 28(5), 1159-1162 (1982)). The pH of the gelatin layer was adjusted to 6.25.
______________________________________ Spreading Layer BaSO.sub.4 Cellulose Acetate Octylphenoxypolyethoxyethanol (Hydroxyethylene Units; 9-10) KH.sub.2 PO.sub.4 Cholesterol esterase Cholesterol oxidase Peroxidase Triarylimidazol leuco pigment Gelatin Layer Gelatin (pH 6.25) Support Transparent polyethylene terephthalate film ______________________________________
In the case of the conventional multilayer analytical element for analysis of cholesterol, the leuco pigment gradually colors during preservation, and therefore, its stability for preservation is inferior. Since this coloration is accelerated in the open air, the analytical element should be used in a short period after opening.